The oxidative dehydrogenation of alkane hydrocarbons or alkyl-containing hydrocarbons to olefinic structures is currently of increasing importance, both for reasons of energy and thermodynamics. Over the past three decades work has appeared from different laboratories describing a group of catalysts such as alumina and various metal phosphates, which are very selective for oxidative dehydrogenation of alkylaromatics such as ethylbenzene to styrene. During this time, evidence has been accumulated that the active site for these catalysts is actually a coke layer which is initially deposited on the surface. The carbon molecular sieves or active carbon have also shown significant activity for these oxidative dehydrogenation reactions. See J. Manassen et al, "Action of Zirconium Phosphate as a Catalyst for the Oxydehydrogenation of Ethylbenzene to Styrene", J. Amer. Chem. Soc., 87, 2671 (1965), G. Emig et al, "Organic Polymers. Correlation Between Their Structure and Catalytic Activity in Heterogeneous Systems. I. Pyrolyzed Polyacrylonitrile and Polycyanoacetylene" J. of Catalysis, 84, 15 (1983) and C. C. Grunewald et al, "Oxidative Dehydrogenation of Ethylbenzene to Styrene Over Carbon-Based Catalysts", J. Molecular Catalysis, 58, 227 (1990).
C. S. Lee U.S. Pat. No. 4,652,690, Mar. 24, 1987, discloses that carbon molecular sieves are catalysts for oxidative dehydrogenation of ethylbenzene to styrene in the presence of oxygen and steam at temperatures of 300.degree. to 400.degree. C. and unspecified pressure.
K. F. Gosselin et al U.S. Pat. No. 3,113,984, Dec. 10, 1963 discloses that carbon molecular sieves are catalysts for oxidative dehydrogenation of alkanes at 900.degree. to 950.degree. F. and unspecified pressure. Since the reaction was done in a Pyrex tube, atmospheric or lower pressure was apparently used.
Aluminum oxide has also been used as a catalyst for oxidative dehydrogenation of hydrocarbons, in T. G. Alkhazov et al, "Oxidative Dehydrogenation of Alkyl Aromatic Hydrocarbons on Aluminum Catalysts. The Nature of the Process of Oxidative Dehydrogenation of Ethylbenzene on Aluminum Oxide", Kinetics i Katalyz., Vol. 14, No. 5, pp 1182-1188 (1973); this reference discloses that aluminum oxide is a catalyst for oxidative dehydrogenation of ethylbenzene to styrene in the presence of air at a temperature of 500.degree. C. and subatmospheric, e.g. 10 torr., pressure.
Although oxidative dehydrogenation usually involves the use of a catalyst, and is therefore literally a catalytic dehydrogenation, oxidative dehydrogenation is distinct from what is normally called "catalytic dehydrogenation" in that the former involves the use of an oxidant, and the latter does not. In the disclosure herein, "oxidative dehydrogenation", though employing a catalyst, will be understood as distinct from so-called "catalytic dehydrogenation" processes in that the latter do not involve the interaction of oxygen in the feed with the hydrocarbon feed. Solid superacids have been disclosed as catalysts for dehydrogenation of hydrocarbons, though not for oxidative dehydrogenation of hydrocarbons. E. J. Hollstein et al U.S. Pat. Nos. 4,918,041, Apr. 17, 1990 and 4,956,519, Sep. 11, 1990, disclose that certain solid superacid compositions, for example sulfated zirconia containing iron and manganese, are suitable for catalyzing the dehydrogenation or partial oxidation of hydrocarbons; no specific dehydrogenation or partial oxidation reactions, nor any conditions for such reactions, are disclosed.